Determine the equilibrium pH of aqueous solutions for the following strong acids

Look for their respective K_a values on net.

 

Not totally relevant to the OP, but part (b) of this exercise is nonsensical in any practical terms. I bring this up because we are in the "Chemistry" forum rather than the "Chemistry Homework" forum.

The answer to a formal calculation to part (b) will only bear any relationship to reality if the concentration of carbon dioxide/bicarbonate in the water is much smaller than that of the hydroxyl -- say 1 nM or less. Any normal aqueous solution will be acting as a carbonate buffer for such low levels of hydroxyl, and I would like to know how anyone proposes to prepare a water sample that is accessible for normal laboratory work, but less than 1 nM in bicarbonate/carbon dioxide.